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<body><span class="vcard"><a class="email" href="mailto:peter.hutterer@who-t.net" title="Peter Hutterer <peter.hutterer@who-t.net>"> <span class="fn">Peter Hutterer</span></a>
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<a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - Lenovo Yoga X1 touchpad unprecise"
href="https://bugs.freedesktop.org/show_bug.cgi?id=99410">bug 99410</a>
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<th>What</th>
<th>Removed</th>
<th>Added</th>
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<td style="text-align:right;">Status</td>
<td>ASSIGNED
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<td>NEEDINFO
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<b><a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - Lenovo Yoga X1 touchpad unprecise"
href="https://bugs.freedesktop.org/show_bug.cgi?id=99410#c7">Comment # 7</a>
on <a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - Lenovo Yoga X1 touchpad unprecise"
href="https://bugs.freedesktop.org/show_bug.cgi?id=99410">bug 99410</a>
from <span class="vcard"><a class="email" href="mailto:peter.hutterer@who-t.net" title="Peter Hutterer <peter.hutterer@who-t.net>"> <span class="fn">Peter Hutterer</span></a>
</span></b>
<pre>ok, I've done an analysis on my T450p which in theory has the same touchpad as
the X1 Yoga. Please attach your dmesg and an evemu-record sequence of such a
circle though so I can verify a few things.
What I found in regards to issue 2 on my touchpad here:
Moving diagonally produces a wavy motion. I can't quite reproduce the circle
here, can you reproduce the wavy motion?
On my device, this is caused by the problem described here:
<a href="https://who-t.blogspot.com.au/2016/09/libinput-and-lenovo-t450-and-t460.html">https://who-t.blogspot.com.au/2016/09/libinput-and-lenovo-t450-and-t460.html</a>
That wavy motion *may* exist on my T440 as well, but it's unclear whether there
it is caused by my finger motion or any other issue. Either way, the same code
and such a pronounced difference hints at a HW/FW bug, see the blog post.
Changing the hysteresis did not have any effect.
The hysteresis is done on a per-axis basis, this could cause the issue you're
seeing. That removing the hysteresis removes the issue verifies this.
Right now I'm assuming that the latest touchpads have a new FW version again
that prevents that bug in the T450p series.
Please remove the call to tp_motion_hysteresis() in libinput's
src/evdev-mt-touchpad.c and try with that version. The diff is:
diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
index e43a9ba..4bac610 100644
--- a/src/evdev-mt-touchpad.c
+++ b/src/evdev-mt-touchpad.c
@@ -1037,7 +1037,6 @@ tp_process_state(struct tp_dispatch *tp, uint64_t time)
tp_thumb_detect(tp, t, time);
tp_palm_detect(tp, t, time);
- tp_motion_hysteresis(tp, t);
tp_motion_history_push(t);
tp_unpin_finger(tp, t);
If this works, we'll probably need a two-pronged approach: make the hysteresis
work across both axes simultaneously and have some knob that exposes it, see
<a class="bz_bug_link
bz_status_NEW "
title="NEW - Somehow conditionalize hysteresis (hardware black/whitelist, device property introspection, user-exposed setting, etc)"
href="show_bug.cgi?id=98839">bug 98839</a>. Removing the hysteresis altogether does not work, see 48473994c8e60
and <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Hard to position a cursor on Thinkad X1 Carbon 3rd gen after f6c2d4b8b5e1968411568d81b47488a655ba47a1."
href="show_bug.cgi?id=94379">bug 94379</a>.
I haven't looked at the pointer acceleration issue (1) yet.</pre>
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